Live Stock. 



312 



[April, 1910. 



lation into cattle and carabaos, con- 

 ferring upon them a period of immunity 

 that may endure from one to four or 

 five months, during which time they 

 will not contract rinderpest even if 

 exposed. It is merely protective, not 

 curative in action, is of no value in any 

 disease but linderpest, and is harmless 

 to any animal. 



The method by which animals prepare 

 substances which are active against 

 disease is a very interesting study, not 

 yet fully solved, and too complex a 

 problem for more than superficial dis- 

 cussion here. A brief mention of the 

 general theory will suffice. It is gener- 

 ally known that following an attack 

 and recovery from an infectious disease, 

 there ensues a period during which the 

 animal is not susceptible to another 

 attack of the same disease. The duration 

 of this immunity varies in the different 

 diseases. Following foot-and-mouth dis- 

 ease the immunity is for but a few 

 months at best, while in rinderpest it is 

 permanent. This immunity is due to 

 the presence in the blood of certain sub- 

 stances called " anti-toxins," substances 

 which have been prepared by the body 

 forces by reason of the stimulation 

 afforded by the presence of the disease 

 germs. These anti-toxins destroy any 

 similar germs that may subsequently 

 enter the body. 



The harmful action of various disease 

 germs is exerted through poisons which 

 they prepare and set free in the body. 

 That is, bacteria, gaining entrance into 

 an animal, do not create disease or cause 

 death mechanically, by reason of their 

 mere physical presence, but by means of 

 poisons, toxins, which they produce. 

 This is true particularly of the more 

 severe diseases of animals and men, such 

 as rinderpest, diphtheria, and tetanus, 

 Similarly, the body in its effort to over- 

 come and eliminate the disease prepares 

 its substances, anti-poisons or anti- 

 toxins, which are poisonous to the bac- 

 teria. The blood-serum and certain forms 

 of cells are credited with the production 

 of these anti-toxins. They are carried in 

 solution in the blood, and circulate into 

 all portions of the body, to encounter 

 and neutralize the toxins, and inhibit 

 the multiplication of the germs. Thus 

 the entrance of disease germs into the 

 body is followed by a struggle between 

 the toxins of thegermsand the anti-toxins 

 prepared by the body. As in auy battle, 

 the issue depends upon the strength and 

 numbers of the combatants. If the 

 bacteria win, the animal dies ; if the 

 body wins, it is because it has prepared 

 sufficiently powerful and numerous anti- 



toxins, set them free in the blood, 

 and thus neutralized the toxins and 



destroyed the germs. 



In rinderpest, the anti-toxins are re- 

 tained indefinitely, circulate in the body 

 fluid and perpetually guard against 

 another infection by rinderpest germs. 

 Not only will these anti-toxins protect 

 the immune animal from the disease, 

 but if his blood be drawn and the serum 

 inoculated into a susceptible animal, it 

 will also serve for the latter's protection. 

 In other words, the anti-toxin is active 

 when withdrawn from recovered animals 

 and injected into others- It is this fact 

 that permits of serum treatment. 



An animal that has just recovered 

 from rinderpest and is therefore immune; 

 is not ready for serum production, as its 

 blood does not contain the requisite 

 number and strength of anti-toxin to 

 protect an animal which is inoculated 

 with a small dose of serum. It is true 

 that if a large amount of blood were 

 drawn, the serum separated and inocu- 

 lated into another animal, the protection 

 afforded would be ample, but this 

 course is not practicable. For economy 

 and convenience it is necessary to pro- 

 duce a powerful serum, so that a 

 small inoculation will furnish the 

 desired degree of protection. In order 

 to accomplish this strengthening of 

 the serum, it is necessary to administer 

 gradually increasing doses of the germs 

 of rinderpest, which, while harmless to 

 the now immune animal, cause him to 

 produce more powerful anti-toxins to 

 neutralize the injected virus. These in- 

 jections are given in a regular series, 

 a regular dose being given each time, 

 until a stage is reached when the animal 

 is considered as fit for serum production 

 and is bled. 



In the preparation of anti-rinderpest 

 serum, practical application is made of 

 this theory. But few animals are 

 immune to rinderpest when admitted 

 into the serum head, so the first step 

 necessary is to pass them through the 

 disease. A mild form of rinderpest is 

 induced by the inoculation of a small 

 amount of virulent blood and a large 

 dose of serum. The serum is given to 

 inhibit the action of the disease, so that 

 the animal will recover after enduring a 

 light attack of rinderpest. The more 

 violent symptoms seldom develop in 

 animals so treated. If the serum were 

 not given, a mortality of about 90 per 

 cent, might be expected, but with its 

 use the percentage is reversed. Usually 

 the disease is in evidence within a 

 week after the injection of virulent 

 blood, and subsides after another ten 

 days. The animal has now experiendce 



